Influence of human wound exudate on the bactericidal efficacy of antiseptic agents in quantitative suspension tests on the basis of European Standards (DIN EN 13727)

Safety and effectiveness of an antiseptic wound cleansing and irrigation solution containing polyhexamethylene biguanide

OBJECTIVE

There is currently a wide range of cleansing and irrigation solutions available for wounds, many of which contain antimicrobial agents. The aim of this study was to assess the safety of HydroClean Solution (HARTMANN, Germany), a polyhexamethylene biguanide (PHMB)-containing irrigation solution, in a standard cytotoxicity assay, and to assess its effect in a three-dimensional (3D) full-thickness model of human skin.

METHOD

A number of commercially available wound cleansing and irrigation solutions, including the PHMB-containing irrigation solution, were tested in a cytotoxicity assay using L929 mouse fibroblasts (ISO 10993-5:2009). The PHMB-containing irrigation solution was then assessed in an in vitro human keratinocyte-fibroblast 3D full-thickness wounded skin model to determine its effect on wound healing over six days. The effect of the PHMB-containing irrigation solution on tissue viability was measured using a lactate dehydrogenase (LDH) assay, and proinflammatory effects were measured using an interleukin-6 (IL-6) production assay.

RESULTS

The PHMB-containing irrigation solution was shown to be equivalent to other commercially available cleansing and irrigation solutions when tested in the L929 fibroblast cytotoxicity assay. When assessed in the in vitro 3D human full-thickness wound healing model, the PHMB-containing irrigation solution treatment resulted in no difference in levels of LDH or IL-6 when compared with levels produced in control Dulbecco's phosphate-buffered saline cultures. There was, however, a pronounced tissue thickening of the skin model in the periwound region.

CONCLUSION

The experimental data presented in this study support the conclusion that the PHMB-containing irrigation solution has a safety profile similar to other commercially available cleansing and irrigation solutions. Evidence also suggests that the PHMB-containing irrigation solution does not affect tissue viability or proinflammatory cytokine production, as evidenced by LDH levels or the production of IL-6 in a 3D human full-thickness wound healing model. The PHMB-containing irrigation solution stimulated new tissue growth in the periwound region of the skin model.

Impact of Interfering Substances on the Bactericidal Efficacy of Different Commercially Available Hypochlorous Acid-Based Wound Irrigation Solutions Commonly Found in South-East Asia

The high prevalence of chronic wounds is a growing concern. Recently, hypochlorous acid (HOCl)-based solutions were introduced as an alternative antimicrobial for wound cleansing. In this study, we assessed the in vitro bactericidal activities of seven commercially available wound irrigation products commonly found in South-East Asia. The evaluation was conducted using quantitative suspension method, EN 13727 in either low or high protein conditions. Under low protein conditions, four out of the five HOCl products achieved bactericidal activity (≥5 log10 reduction factor; RF) within 2-5 min, and only one product achieved 5 log10 RF at 15 s. None of the HOCl achieved 5 log10 RF under high protein, even after 30 min of exposure time. In contrast, protein interference on the antimicrobial activities of polyhexamethylene biguanide-based product is less pronounced (low protein: 60 s vs. high protein: 2 min to attain ≥5 log10 RF). Octenidine dihydrochloride is the only active not affected by protein interference achieving ≥5 log10 RF within 15 s in both low and high protein conditions. These findings warrant the need to screen antimicrobial wound care products, especially HOCl-based products, in high protein condition to better reflect the antimicrobial activities in wound care.

Hydrogel Encapsulating Wormwood Essential Oil with Broad-spectrum Antibacterial and Immunomodulatory Properties for Infected Diabetic Wound Healing

The integration of hydrogels with bio-friendly functional components through simple and efficient strategies to construct wound dressings with broad-spectrum antibacterial and immunomodulatory properties to promote the healing of infected diabetic wounds is highly desirable but remains a major challenge. Here, wormwood essential oil (WEO) is effectively encapsulated in the hydrogel via an O/W-Pickering emulsion during the polymerization of methacrylic anhydride gelatin (GelMA), acrylamide (AM), and acrylic acid N-hydroxysuccinimide ester (AAc-NHS) to form a multifunctional hydrogel dressing (HD-WEO). Compared with conventional emulsions, Pickering emulsions not only improve the encapsulation stability of the WEO, but also enhance the tensile and swelling properties of hydrogel. The synergistic interaction of WEO's diverse bioactive components provides a broad-spectrum antibacterial activity against S. aureus, E. coli, and MRSA. In addition, the HD-WEO can induce the polarization of macrophages from M1 to M2 phenotype. With these advantages, the broad-spectrum antibacterial and immunomodulatory HD-WEO effectively promotes the collagen deposition and neovascularization, thereby accelerating the healing of MRSA-infected diabetic wounds.

Impact of human wound exudate on the bactericidal efficacy of commercial antiseptic products

OBJECTIVE

By default, the antimicrobial efficacy of antiseptics used in wound management is tested in vitro under standardised conditions according to European standard DIN EN 13727, with albumin and sheep erythrocytes used as organic challenge. However, it is not clear whether these testing conditions adequately reflect the wound bed environment and its interaction with antiseptic products intended to be used in wounds in humans.

METHOD

This study compared the efficacy of different commercial antiseptic products based on octenidine dihydrochloride (OCT), polyhexamethylene biguanide (PHMB) and povidone-iodine under challenge with human wound exudate collected from the hard-to-heal wounds of patients, compared to the standardised organic load, in an in vitro setting according to DIN EN 13727.

RESULTS

The bactericidal efficacy of the tested products was reduced to a different extent when challenged with human wound exudate, compared to the standardised conditions. Overall, OCT-based products showed the necessary germ count reductions at the shortest exposure times (e.g., 15 seconds for Octenisept (Schülke & Mayr GmbH, Germany)). PHMB-based products were the least efficient. In addition to the protein content, other components of wound exudate, such as the microbiota, seem to influence the efficacy of antiseptics.

CONCLUSION

This study demonstrated that the standardised in vitro test conditions may only partially reflect actual wound bed conditions in humans.

Composition of Challenge Substance in Standardized Antimicrobial Efficacy Testing of Wound Antimicrobials Is Essential to Correctly Simulate Efficacy in the Human Wound Micro-Environment

Current standards insufficiently acknowledge the influence of the wound micro-environment on the efficacy of antimicrobial agents. To address this, octenidine/phenoxyethanol, polyhexanide, povidone-iodine, and sodium-hypochloride/hypochlorous acid solutions were submitted to standard-based (DIN-EN-13727) or modified peptide-based challenges and compared to a simulated clinical reference using human acute or chronic wound exudate (AWF/CWF). Antimicrobial efficacy against S. aureus and P. aeruginosa was compared using a quantitative suspension method. Agreement between methods were investigated using Bland-Altman (B&A) analysis. Different substances and challenges demonstrated diverging results, depending on class and concentration of agent and challenge. Highly concentrated antiseptics maintained a high efficacy under complex challenges, while especially chlorine-based irrigation solutions showed a remarkably reduced antimicrobial effect. Composition of challenge substance proved more relevant than pure concentration. Therefore, the current standard challenge conditions did not adequately reflect the wound micro-environment with over- or under-estimating antimicrobial efficacy, whilst the modified peptide-challenge showed a higher level of agreement with simulated realistic conditions (AWF/CWF). The results emphasize that a "one-fits-all" approach is not feasible to generalize antimicrobial efficacy, as certain aspects of the complex micro-environment pose a differing influence on varying agents. Based on these results, revision and target focused adaptation of the current standards should be considered.

Bimetallic silver-platinum (AgPt) nanoparticles and chitosan fabricated cotton gauze for enhanced antimicrobial and wound healing applications

Wound healing is a significant clinical and socioeconomic problem that is often affected by microbial infection. Inappropriate monitoring leads to unfavorable concerns for surrounding tissues. Cotton gauzes have been used as low-cost wound dressing material but prolong healing owing to strong adherence and secondary microbial infections. Hence, we prepared the bimetallic (silver and platinum) nanoparticles (AgPt NPs) using citric acid (CA) as a reducing agent and then coated them on chitosan (CS) fabricated cotton gauze (CG) for enhanced antimicrobial and wound healing applications. The synthesis of AgPt NPs was evidenced UV-Visible spectroscopy, FE-TEM, and elemental mapping analysis. The average size of AgPt NPs was 21.48 ± 6.32 nm and spherical in structure. Besides, AgPt NPs showed a hydrodynamic size of 63.64 (d.nm) with a polydispersity index of 0.220 and a zeta potential of -28.1 mV. The FT-IR and XRD analysis demonstrated the functional changes and crystalline properties of AgPt NPs. The antimicrobial efficacy of AgPt NPs was significantly higher than standard antibiotic against bacteria, yeast, and filamentous fungi. Furthermore, the AgPt NPs-CS/CG exhibited a substantial hydrophobic nature with better antimicrobial and antioxidant activity. In addition, pH-dependent Ag and Pt release from the AgPt NPs-CS/CG was determined by ICP-MS analysis. The treatment of AgPt NPs-CS/CG augmented the in vitro wound healing in mouse embryonic fibroblast cells (NIH3T3). Hence, we concluded that AgPt NPs-CS/CG could be used to enhance antimicrobial and wound healing applications.

rhEGF-Loaded Hydrogel in the Treatment of Chronic Wounds in Patients with Diabetes: Clinical Cases

The aim of the study was to evaluate the healing process of chronic wounds treated with carboxymethylcellulose loaded with recombinant human epidermal growth factor in patients with diabetes. The case series consisted of 10 patients treated at the university hospital for 12 weeks. Data were analyzed using SPSS version 22.0. according to the intention to treat the principle, without the loss or exclusion of the participants. The sample consisted of 70% (7/10) males with a mean age of 61.9 years (±9.4); all (100%) had diabetes mellitus and 70% (7/10) had systolic hypertension associated with diabetes mellitus. Sixty percent (6/10) presented lesions of diabetic etiology and 40% (4/10) presented lesions of venous etiology; 70% (7/10) had had lesions for less than 5 years. The mean glycated hemoglobin was 7.8% (±2.7%), while the mean ankle-arm index (AAI) was 0.94 (±0.21). The mean initial area of all wounds was 13.4 cm², and the mean final area was 7.8 cm², with a reduction rate of 28.9% over the 12 weeks of treatment. The reduction rate of diabetic ulcers was higher (33.4%) than that of venous ulcers (22.1%). Regarding the type of tissue, there was an increase in granulation and epithelialization, and a decrease in slough and the amount of exudate that were statistically significant (p = 0.021). No participant had severe or local adverse events during the study period. Epidermal growth factor was effective in the treatment of chronic wounds, especially diabetic ulcers, resulting in the reduction of the wound area and the improvement of tissue and exudate quality.

The application of normative documents for determination of biocidal activity of disinfectants and antiseptics dedicated for medical area: a narrative review

Disinfectants and antiseptics are important weapons to reduce the number of microorganisms and thus to limit the number of infections. Different methods of antimicrobial activity testing, often not standardised, without appropriate controls and not validated are applied. To address these issues, several European Standards (EN) have been developed, describing the test methods to determine whether chemical disinfectants or antiseptic products have appropriate bactericidal, sporicidal, mycobactericidal or tuberculocidal activity; fungicidal or yeasticidal activity; or virucidal activity. In this narrative review, the 17 EN concerning evaluation of the above-mentioned antimicrobial activity of preparations dedicated to the medical area are briefly reviewed, together with recent publications on this topic. Suspension and carrier tests have been performed in clean and dirty conditions simulating the medical area. In addition, a wide range of applications of these standards has been presented in the research of biocides for hand antisepsis, surfaces disinfection, including airborne disinfection as well as medical device and medical textile disinfection. The role of normative documents in the investigation of antimicrobial activity of disinfectants and antiseptics to limit infections has been underestimated. This narrative review aims to persuade researchers to conduct antimicrobial activity testing in line with validated EN and highlights an existing gap in ongoing research. It also aims to raise awareness of the wide range of biocidal activity tests with standardised methods in medical area. We also pay attention to the recently developed European Pharmacopoeia monography concerning the testing of bactericidal and fungicidal activity of antiseptics classified as medicinal products.

The High Impact of Staphylococcus aureus Biofilm Culture Medium on In Vitro Outcomes of Antimicrobial Activity of Wound Antiseptics and Antibiotic

The staphylococcal biofilm-based infections of wounds still pose a significant therapeutical challenge. Treated improperly, they increase the risk of limb amputation or even death of the patient. The present algorithms of infected wound treatment include, among others, the application of antiseptic substances. In vitro wound biofilm models are applied in order to scrutinize their activity. In the present work, using a spectrum of techniques, we showed how the change of a single variable (medium composition) in the standard in vitro model translates not only to shift in staphylococcal biofilm features but also to the change of efficacy of clinically applied wound antimicrobials such as octenidine, polyhexamethylene biguanide, chlorhexidine, hypochlorite solutions, and locally applied gentamycin. The data presented in this study may be of a pivotal nature, taking into consideration the fact that results of in vitro analyses are frequently used to propagate application of specific antimicrobials in hospitals and ambulatory care units.

Effectiveness of a synthetic human recombinant epidermal growth factor in diabetic patients wound healing: Pilot, double-blind, randomized clinical controlled trial

To investigate whether the addition of human recombinant epidermal growth factor (h-EGF) to 2% carboxymethyl cellulose gel is more effective in diabetic wound healing than standard treatment, a pilot, double-blind, randomized and controlled clinical trial with therapeutic intervention was performed at a university hospital. The sample consisted of 25 patients (14 in the intervention group that used rh-EGF and 11 in the control group that used 2% carboxymethyl cellulose gel). Data were tabulated in SPSS and analysed by intention to treat, without loss or exclusion of participants. Twenty-five subjects participated with a mean age of 60.6 years, a predominance of males in both groups and 100% prevalence of type-2 diabetes. Within 12 weeks, complete wound healing occurred in three ulcers in the intervention group versus one ulcer in the control group. The percent reduction in the wound area was significantly higher in the intervention group than in the control group (p = 0.049). Concerning the types of tissue, an increase in granulation and epithelial tissue and a reduction in exudate levels were observed in both groups. Decreased slough occurred only in the intervention group. No participant experienced serious or local adverse events during the study period. This study shows that h-EGF is effective, with a statistically significant reduction in wound area, improvement of tissue quality, and safe treatment of chronic wounds. In addition, this study demonstrated that blinding of participants during research using h-EGF is feasible.

Inhibitory effect of host ocular microenvironmental factors on chlorhexidine digluconate activity

Acanthamoeba spp. are free-living protozoan that cause a serious human eye disease called Acanthamoeba keratitis (AK). Several new and effective medical therapy for AK patients remains highly debated and therefore, CHG is still considered one of the first lines of treatment for AK patients. We hypothesized that ocular microenvironmental factors are responsible for Acanthamoeba drug resistance and clinical AK treatment failure. To investigate the influence of the ocular surface on CHG treatment, we tested the effect of several ocular elements on the anti-amoeba activity of CHG. The suspected inhibitory elements, including mucin, albumin, human and amoeba cell lysates, live and heat-killed bacteria, and cornea, were added to the amoebicidal activity platform, where amoeba was incubated with CHG at varying concentrations. Mucin showed a significant inhibitory effect on CHG activity against Acanthamoeba castellanii In contrast, albumin did not affect CHG treatment. Furthermore, human and amoeba cell lysates as well as live and heat-killed bacterial suspensions also significantly inhibited CHG activity. Additionally, we found that pig corneas also reduced CHG activity. In contrast, dry eye drops and their major component, propylene glycol, which is commonly used as eyewash material, did not have an impact on CHG activity. Our results demonstrate the effect of ocular microenvironmental factors on CHG activity and suggest that these factors may play a role in the development of amoeba resistance to CHG and treatment failure.

Antimicrobial Hypochlorous Wound Irrigation Solutions Demonstrate Lower Anti-biofilm Efficacy Against Bacterial Biofilm in a Complex in-vitro Human Plasma Biofilm Model (hpBIOM) Than Common Wound Antimicrobials

Biofilms pose a relevant factor for wound healing impairment in chronic wounds. With 78% of all chronic wounds being affected by biofilms, research in this area is of high priority, especially since data for evidence-based selection of appropriate antimicrobials and antiseptics is scarce. Therefore, the objective of this study was to evaluate the anti-biofilm efficacy of commercially available hypochlorous wound irrigation solutions compared to established antimicrobials. Using an innovative complex in-vitro human plasma biofilm model (hpBIOM), quantitative reduction of Pseudomonas aeruginosa, Staphylococcus aureus, and Methicillin-resistant S. aureus (MRSA) biofilms by three hypochlorous irrigation solutions [two <0.08% and one 0.2% sodium hypochlorite (NaClO)] was compared to a 0.04% polyhexanide (PHMB) irrigation solution and 0.1% octenidine-dihydrochloride/phenoxyethanol (OCT/PE). Efficacy was compared to a non-challenged planktonic approach, as well as with increased substance volume over a prolonged exposure (up to 72 h). Qualitative visualization of biofilms was performed by scanning electron microscopy (SEM). Both reference agents (OCT/PE and PHMB) induced significant biofilm reductions within 72 h, whereby high volume OCT/PE even managed complete eradication of P. aeruginosa and MRSA biofilms after 72 h. The tested hypochlorous wound irrigation solutions achieved no relevant penetration and eradication of biofilms despite increased volume and exposure. Only 0.2% NaClO managed a low reduction under prolonged exposure. The results demonstrate that low-dosed hypochlorous wound irrigation solutions are significantly less effective than PHMB-based irrigation solution and OCT/PE, thus unsuitable for biofilm eradication on their own. The used complex hpBIOM thereby mimics the highly challenging clinical wound micro-environment, providing a more profound base for future clinical translation.

Influence of human wound exudate on the bactericidal efficacy of antiseptic agents in quantitative suspension tests on the basis of European Standards (DIN EN 13727)

The antimicrobial efficacy of antiseptics used in wound management is tested in vitro under standardised conditions according to DIN EN 13727, with albumin and sheep erythrocytes used as organic challenge. However, these testing conditions do not adequately simulate the wound bed environment. Thus, the aim of this study was to compare the efficacy of different antiseptics such as octenidine dihydrochloride (OCT), chlorhexidine digluconate (CHX), polyhexamethylene biguanide (PHMB), and povidone-iodine under challenge with human wound exudate instead of standardised organic load in an in vitro setting according to DIN EN 13727. Moreover, protein contents, pH, and temperature were compared with standardised testing conditions. The tested antiseptic agents were reduced to different extents based on their bactericidal efficacy, when challenged with human wound exudate compared with standardised conditions. Overall, 0.10% OCT showed the highest effects reaching full efficacy after 30 seconds. CHX and PHMB were the least efficient. Next to the protein content, other components of wound exudate, such as the microflora, seem to influence the efficacy of antiseptics. In summary, the optimisation of in vitro testing conditions in future applications, to more adequately simulate the wound bed environment, will allow a more realistic picture on the potential performance of antiseptics in clinical practice.